Production of cube-on-edge oriented siliconiron

ABSTRACT

An improvement in the production of cube-on-edge silicon-iron comprising the step of heating the silicon-iron having an oxygen content no greater than 0.0045 percent to a temperature of from 2,100*F. to not more than 2,400*F. immediately prior to hot rolling.

United States Patent Kohler et al.

[111 3,802,937 1 1 Apr. 9, 1974 PRODUCTION OF CUBE-ON-EDGE ORIENTEDSILICON-IRON [75] Inventors: Dale M. Kohler; Martin F.

Littmann, both of Middletown, Ohio [73] Assignee: Armco SteelCorporation,

Middletown, Ohio [22] Filed: Sept. 30, 1966 [21] Appl. No.: 583,459

[52] U.S. Cl 148/111, 148/3155, 148/110, 148/112 [51] Int. Cl...H01f1/04 [58] Field of Search 148/31.55, 110,l11,112

[56] References Cited UNITED STATES PATENTS 2,599,340 6/1952 Littmann148/111 2,826,520 3/1958 Rickett 148/111 2,867,557 1/1959 Crede 148/1113,105,782 10/1963 Walter 148/111 X 3,305,354 2/1967 Boni et al. 148/31553,333,991 8/1967 Kohler 148/111 3,333,992 8/1967 Kohler 148/1113,345,219 10/1967 Detert 148/111 Primary Examine -L. Dewayne RutledgeAssistant Examiner-W. R. Satterfield Attorney, Agent, or Firm-Me1ville,Strasser, Foster & Hoffman 5 7 ABSTRACT An improvement in the productionof cube-on-edge silicon-iron comprising the step of heating thesiliconiron having an oxygen content no greater than 0.0045 percent to atemperature of from 2,100F. to not more than 2,400F. immediately priorto hot rolling.

8 Claims, No Drawings PRODUCTION OF CUBE-ON-EDGE ORIENTED SILICON-IRONThis invention relates to a method of producing grain-orientedsilicon-iron sheet or strip for magnetic purposes. The grain orientationto which this invention refers is that wherein the body-centered cubesmaking up the grains or crystals are oriented in the cube-onedgeposition, designated (110) [001] in accordance with the Miller lndices.More specifically, this invention relates to an improved and economicalmethod of producing grain-oriented silicon-iron, whereby the temperaturerange to which the silicon-iron is heated prior to hot rolling islowered by maintaining the oxygen content of the silicon-iron below acritical lower limit.

As is well known, silicon-irons having the (1 [001] orientation arecharacterized by a relatively high permeability in the rolling directionand a relatively low permeability in a direction at a right anglethereto. A commercial product of this nature has been used successfullyfor many years for the manufacture of laminations or cores intransformers, generators and the like, because of its low coreloss andhigh permeability in the rolling direction.

The greater part of the cube-on-edge'oriented silicon-iron sheet stockis currently made from the raw materials by a number of steps whichinclude melting, refining, casting and hot rolling ingots or slabs of asuitable composition to hot bands usually less than 0.1 inch thick.Following annealing and pickling steps, the material is cold rolled inone or more stages with intermediate anneals, subjected to adecarburizing step, and finally annealed at a temperature high enough tocause secondary recrystallization. The secondary recrystallization hasbeen of the grain boundary energy type.

As indicated above, current practice begins the hot rolling step eitherwith a slab or directly with an ingot. In the first instance an ingot iscast. The ingot is soaked at a high temperature of about 2,200 F. to2,300 F. for several hours in order to equalize the ingot temperature toobviate problems caused by differential cooling in the ingot. The ingotis then rolled into a slab, generally about 6 inches thick, and allowedto cool slowly.

Prior to the hot rolling step, the slab is reheated to about 2,500 to2,550 F.

When direct hot rolling from an ingot is practiced, it is'usual to castan ingot and soak it at about 2,45.0 F. prior to the hot rolling step.

The temperature to which a slab is reheated or an ingot is heated priorto the hot rolling step has been the subject of much study among priorart workers. It was taught by Goss in US. Pat. No. 2,084,337, issuedJune sally by the industry. Such extremely high temperaposal of slagwhich forms on the slabs or ingots when they are heated above about2,400 F. This slag comprises liquid oxide formed by the oxidation of thesurface of the slab. Accumulation of this slag eventually interfereswith the operation of the slab or ingot heating furnace and it becomesnecessary to take the furnace out of operation in order to remove theslag. Because of the dependence of the hot rolling mill on a steadysupply of slabs or ingots, the output of the hot mill is severelycurtailed each time a furnace is down for repairs. In fact, theproduction of the entire steel making facility is affected. In additionto costly shutdowns because of slag accumulation, such high temperaturesincur higher heating costs, and require more expensive heatingequipment. The high temperatures and corrosive effect of the slaggreatly reduce furnace refractory life. Nevertheless, all of thesedisadvantages 22, 1937, that the ingot should be heated to about 2,000F. or above, and the reduced slab should be heated to about 2,000 F.Although silicon-iron may be rolled at a temperature as low as 2,000 E,the final product does not exhibit good magnetic qualities.

Littmann and Heck in US. Pat. No. 2,559,340, issued June 3, 1952, taughtthat superior permeabilities could be obtained in silicon-iron by hotrolling from a high initial temperature. They discovered that themagnetic properties of nominal 3 percent silicon-iron would be muchimproved if the ingot or reheated slab were taken to a temperature aboveabout 2,300 F. and up to about 2,5 F. (or the highest temperaturepossible without burning) prior to the hot rolling step. As indicatedabove, this teaching has been adopted univerhave been consideredunavoidable and the expense entailed thereby has been considerednecessary in order to produce silicon-iron of the highest quality.

It was taught by Rickett in US. Pat. No. 2,826,520 issued Mar. ll, 1958,that the slag problem could be eliminated by heating the slabs withinthe limited temperature range of 2,225 F to 2,275 F. for a minimum of 8hours. However, this method has not been adopted commercially and theproductproduced thereby is not characterized by high magnetic qualitiesWhile all of the work represented by the aforementioned. patentsconcerned so-called critical ranges within the broad general range ofslab heatingtemperatures, for commercially produced silicon-iron alloyscontaining the standard elements, none was dependent upon nor related tothe oxygen content which normally exceeded 0.005 percent, and often wasas high as 0.010 percent.

, It may be seen from the foregoing discussion of the prior art thatthere are different and sometimes conflicting teachings as to the mostdesirable temperatures for the ingot and slab heating steps in theproduction of grain oriented silicon-iron. It is therefore a primaryobject of the present invention to provide a method of producingcube-on-edge oriented silicon-iron whereby the slab or ingot temperatureprior to the hot rolling step has been rendered nugatory in relation tothe quality of the final product.

It is also a primary objectof the present invention to provide a moreeconomical method for the manufac, ture of cube-on-edge silicon-ironwhereby savings are realized both in the processing of the 'materialandin the less severe conditions affecting the apparatus or equipment used.in its manufacture.

It is an object'of the present invention to providesuch a method withoutsacrificing the high standards allow its metallurgical structure to becontrolled at each step of the process.

These and other objects of the invention which will be set forthhereinafter or will be apparent to one skilled in the art upon readingthese specifications are inhibitor of normal grain growth must beprovided in order to promote secondary growth of the decarburized,primary recrystallized structure during the final I high temperatureanneal. While a number of inhibitors such as manganese selenide may beused, for purposes of an exemplary showing the process of the presentapplication will bedescribed in terms of manganese sulfide as theinhibitor. I

. It is known that when the manganese sulfide, in the I amount formed byhaving the manganese and sulfur contents in the ranges given below, iswell dispersed as submicroscopic precipitates in the silicon-iron, theseprecipitates will inhibit primary grain growth followingrecrystallization after cold rolling. Thus, during the final anneal ofthe material, the secondary grains which start to grow at about 1,700 F.can engulf the primary grains to produce the desired cube-on-edgeorientation.

I It has been discovered that when the oxygen content of thesilicon-iron is kept within the limits given below,

. a better performance from the manganese sulfide inhibitor isobtainable, and high slab'or ingot temperatures are not required. Infact, slab or ingot tempera-' tures may be used which are below whatwould normally be thought to be the temperature at which the majority ofthe manganese sulfide would go into solution. The reason for this is notfully understoodnwhile not intending to be bound by theory, it isbelieved that the silicon-iron of the present invention, having the lowoxygen content givenbelow, may naturally give a finer dispersion of thesulfide phase because of the absence of oxide nucleation sites. I v

In the practice of the present invention, the composition of thesilicon-iron is critical. The amount of oxygen should not exceed 0.0045percent and'preferably' should not exceed 0.0030 percent. The vmanganesecontent; should be from about 0.03 percent to about. 0.08 percent, andpreferably from about 0.045 percent to about 0.065 percent. The lowerlimit is determined by the amount of manganese necessary to form asufficient quantity of manganese sulfide to act as a grain growthinhibitor; The upper limit is determined by the solubility of themanganese sulfide prior to hot rolling, the higher manganese causing thesulfide tobe less soluble. Also, higher manganese contents render sulfuradditions to the silicon-iron at later stages of the processinglesseffective. Initial sulfur should be presentin about 0.025 percent.Selenium may be substituted for tial carbon content should be from about0.015 percent to about 0.035 percent, and preferably from about 0.020percent to about 0.030 percent. The silicon con tent may be from about1.8 to '4 percent or higher, the lower limit being the minimum siliconwhich will avoid a phase change to gamma iron upon heating, while theupper limitisdependent upon the ability of the material to be coldrolled without breakage. The nitrogen content should not exceed about0.007 percent and preferaly should not exceed about 0.004 percent. Nomore than about 0.008 percent total aluminum should be present. It ispreferred to have thatv portion of the aluminum present in theacid-soluble form constitute less than 0.002 percent.

To obtain the critical oxygen content of the present invention, any lowoxygen refining process may be used, including vacuum techniques. Oneprocess, which has the advantage of being amenable to the use ofexisting apparatus such as the open hearth or electric furnace, isdisclosed by Boni and Heck, U.S. Pat. No. 3,305,354. The re-ladlingprocess of their invention is capable of removing oxygen to a level ofabout ten parts per million or 0.001 percent. v

The silicon-iron having the melt composition given above may beconventionally cast into ingots or it may be continuously. cast intoslab-ingots. Hereinafter the use of the terms slabs and ingots isintended to in- I clude silicon-iron which has been continuously cast.

Prior to the step of rolling to hot bands, the siliconiron will beheated whether it be in ingot form (where direct rolling to strip isusedlor slab form (where a reheating step is practiced). In accordancewith the presentinvention, the slabs or ingots are heated to within atemperature range between the lowest temperature at which the ingots orslabs are workable and the highest temperature at which no appreciableamount of slag will be formed. Conventionally the slabs will be held attemperature for a period of less than one hour, while ingots aregenerally soaked for several hours.

While slabs or' ingots are workable in .the laboratory at temperaturesas low as 1,800" F.', it has been found that the lowest practicaltemperature under plant processing conditions is about 2,l00 F.

The highest temperature at which no appreciable amount of slag will beformed is dependent upon a number of factors. These factors include timeat temperature, atmosphere,- type of flame and the like. Nevertheless,it has been determined thatlthe above depractice of the presentinvention, the temperature at which the hot rolling is completed is notconsidered to be critical in and of itself. It is preferred that thefinish-' ing temperature be above 1,650 P. Similarly, the coilingtemperature has not been found to be extremely critical. A temperatureof about 1,200 F. is normal. The steps of the process following hotrolling are conventional. The hot band may be annealed before it is coldrolled in order to improve the structure. If an initial anneal is used,the temperature may vary from about 1,650 F. to about 2,000 F., andpreferably is about l,800 F., for a time of up to about four minutes attemperature.

Oriented silicon-iron having a final thickness of ent invention, theteachings herein are particularly ap-- plicable to the production oforiented silicon-iron having a final thickness of about 0.014 inch orless.

The silicon-iron will be decarburized to a value of 0.003 percent orless during one or more of the anneals. This may be done in anatmosphere such as wet hydrogen.

After decarburization, the strip is generally coated with an annealingseparator and box annealed for at least 8 hours at a minimum temperatureof 2,000 F. Higher temperatures and longer times at temperature are usedwhen it is necessary to remove sulfur or other undesirable impurities.The sulfur content will be reduced to less than 0.002 percent during thefinal anneal.

Various modifications may be made in the processing steps following thehot rolling withoutdestroying the beneficial effects imparted by theparticular composition of the silicon-iron and especially its oxygencontent. Therefore, it will be understood that the processing of thematerial beyond the hot rolling stage has been described as exemplaryand does not constitute a limitation upon the invention.

When the oxygen content of the silicon-iron, which may be from a traceto 0.0045 percent is in the upper portion of this range, andparticularly when it is above about 0.0030 percent, it may be founddesirable to heat the ingots or slabs to a temperature within the upperportion of the above given range, i.e. to a temperature from about 2,300F. to about 2,400 F.

It is a feature of the present invention that the siliconiron sheetstock may be treated at final gauge, and immediately prior to or duringthe primary grain growth portion of the final anneal, with sulfur,selenium or their compounds from an external source. The use of sulfuris preferred'for economic reasons. The sulfur- 6 to hot rolling, willyield a product having excellent magnetic properties. For example, whenthe oxygen content of the silicon-iron is within the upper part of theabove given range, the addition of sulfur from an external source willinsure an excellent product even at a slab or ingot heating temperatureof 2,l00 F.

As a non-limiting example silicon-iron of the above outlined compositionin the form of slabs or ingots may be heated within the range of 2, 100F. to 2,400 F. and rapidly rolled to the desired hot band thickness. Ifan initial anneal is used the temperature may vary from about l,650 F.to about 2,000 F. for a time of up to about four minutes at temperature.When a final product about 0.012 inch'thick is desired, the silicon-ironwill be cold rolled in a first stage to an intermediate gauge of about0.030 inch. This will be followed by an intermediate anneal at about1,700 F., and a second stage of cold rolling to final gauge. Thematerial may then be decarburized as described above. Sulfur from anexternal source may be added in any of the ways and in an amount astaught in .the above mentioned Kohler patents, and the material will besubjected to a final box anneal at a minimum temperature of 2,000 F. forat least 8 hours. Again, with respect to the final anneal, highertemperatures and'longer times atv temperatures will be used if it isnecessary to remove sulfur or other undesirable impurities. I

The addition of sulfur from an external source in the process of thepresent inventionwill also serve to insure a product of excellentmagneticqualities when a single stage cold rolling step is used. Theprocess will be substantially the same as that just described exceptthat the desired final gauge is achieved by a single cold rolling may beadded in the ways taught by Kohler in US. Pat.

Nos. 3,333,991 and.3,333,992. As taught in these patents the sulfuraddition maybe made in several ways. For example, sulfur orsulfur-bearing compounds may be added to the annealing separator in thefinalanneal. Similarly, the annealing atmosphere of the final anneal maybe charged with a gaseous sulfur compound providing the atmosphere is incontact with the surfaces of the silicon-iron. In yet another variant,sulfur or sulfurbearing compounds may be made available at the surfacesof the sheet material during a decarburizing anneal prior to the finalanneal.

The practice of the present invention requires accurate melting andaccurate chemical analysis. While the degree of accuracy both in meltingand in chemical analysis in plant processing is increasing rapidly, itis often not possible to achieve the degree of accuracy in plantprocessing that is obtainable in the laboratory. It has been found thatin some instances the addition of sulfur from an external source willserve as insurance that the silicon-iron of the present invention, whenheated within the above given temperature rangeprior stage.

Three slabs (hereinafter designated A, B and C) about 6 inches thickwere selected from a heat of silicon-ironwhich had been melted in anopen hearth using the previously mentioned method of Boni and lastreduction. The ceiling temperature for all three slabs, which wasregulated by the amount of water sprayed on the strip, was about l,200F. and the hot band thickness was about 0.080 inch. The hot rolled bandswere annealed at l,800 F. j

The hot rolled bands were then cold rolled to 0.030

inch, strip annealed at 1,700 F., cold rolled to 0.012

TABLE I Slab Slab Core Losses Number mp r Permeability Pl;60 w/lb.Pl7;60 w/lb.

A 2550 F. 183i .575 .803 a 2400 F. 1833 .566 .793 c 2100" F. 1823 .553.785

It may be seeiifi rn 5155560315150 015i iii; narrate properties of thematerial which had been hot rolled from widely different temperaturesare surprisingly comparable.- Whereas the permeability of the 2,100 F.material is substantially the same, the corresponding core losses areslightly better than those for material rolled from the highertemperatures. It may be said that the provision of a silicon-iron of aninitial composition within the above described limits, and particularlywith a very low oxygen content, has made the slab temperature nugatoryin relation to the quality of the product- Of course, it is usuallybetter from a cost consideration to use the lowest temperatureconsistent with mill practices. For instance, when silicon-iron slabsare being heated with slabs of carbon steel or stainless steel, it

- would be more practical to heat the silicon-iron slabs Thepermeability values show that the low oxygen content of the hot rolledband is strongly associated with high permeability. These values alsoindicate that,

as the oxygen content increases, the permeability decreases more rapidlywhen the-initial annealing temper- .......5XMPPE11 Two slabs about sixinches thick representing two ingots were selected at random from eachof two heats having ladle analyses as follows;

Heat Number %Mn 708 %Si %N %O 7 %Al (total) %C A .026 .066 .023 3.21,.0052 .0070 .0053 B .053 .023 3. l 3 f .0057 .0023 .006l

to the temperature range dictated by the other materials. 3

EXAMPLE n about three minutes in air. All of the samples were thenprocessed to a final thickness of 0.012 in two stages of cold reduction.I

The samples were annealed at 1,675 F. in hydrogen for about 1 minute attheir intermediate thickness of 0.026 inch. After the secondcoldrolling, they were decarburized at 1,500 F. for about three minutesin wet hydrogen and given a final box anneal at 2,200 F. in

hydrogen for 24 hours.

Table II shows the initial compositions and final per meability valuesfor the materials given the two initial annealing temperatures. r

ck. Essentially no liquid slag was formed. The temperature immediatelyafter hot rolling was about l,800 F. and .the strip was coiled at about1,200 F. The hot bands were strip annealed at 1,675 F. for about oneminute, pickled and cold rolled to 0.024 inch. After an intermediateanneal at 1,700? P. the coils were cold rolled to about 0.0105 inch,strip decarburized, coated with magnesia, and annealed at 2,200 F. for24-hours in a'hydrogen'atmosphere. The magnetic properties are shown inTable III and illustrate the value of low oxygen in attainingexcellenrmagnetic quality. Table III is divided into two parts, eachrelating to one of the heats. Within each part the first three values ineach column refer to samples from the front, middle and back of the coilfrom the first slab of the respective heat. Similarly the next threevalues represent samples from the front, middle and back of the coilfrom the second slab of the same heat. The last valueis an average ofthe values. of all six samples.

TABLE ll 1675 F. l800 F. initial Anneal Initial Anneal PermeabilityPermeability Slab %C %Mn 705 %O %N H =10 H.= H)

A .022 V .059 .022 .00l5 .0057 i771 l79l B .023 .060 .024 .0019 .0057l73 l I797 C ,0l6 .062 (H8 .0030 .0030 N376 1761 D .0l9 .062 .(ll) .0050.0054 164i I747 E .023 .043 .016 .0076 .0074 1596 i706 TABLE 111 HEAT A(.0070% O) EXAMPLE v One slab six inches thick from each of fourdifferent heats was reheated to a temperature of 2,l F. and

Thickhot rolled into coils 0.076 inch thick. Samples were 3? Perm takenfrom the centers of these coils and processed in M11. Pl5;60 w/lb.Pl7;60 w/lb. 1-1=10. the laboratory. The samples were annealed at l,800F. 11.0 .500 .725 l825 for about 3 minutes, cold rolled directly to0.012 inch 8% g; 3%? :23? 1 without an intervening anneal, decarburizedin a strip 105 I555 1900 1740 anneal in wet hydrogen at l,500 F., coatedwith'mag- 88 228 {3 nesia with and without sulfur, and box annealed inhydrogen at 2,200 F. for 30 hours. The permeability val- 10.5 .552 .863172 A e g ues obtained are shown below in Table V together with theanalyses of thehot rolledsamples.

TABLE V NO Sulfur 4% Sulfur Added to MgO Added to MgO Slab %c %Mn %s 7.0%N Perm.H 10 Perm H= 10 A .022 .059 .022 .0015 .0057 I 1605 e 1770 B.022 i .060 .023 .0018 .0057 1625 1745 c .024 .048 .017 .0065 .0076 15521665 D .021 .069 .020 .0090 .0050 1590 1632 HEAT B .0023% 0) 7 Thesedata showthat a sulfur addition to the magne- Thicb sia is rendered moreeffective when the oxygen content ness is maintained within the criticalrange of the invention. The test results for the materials to whichsulfur has M115 P15;60 w/lb. P17;60 w/lb. 1-1 =10.

been added represent excellent magnetic quality, when 10.6 .520 .76018l5 it is considered that only a single cold reduction was 10.4 .500.740 1820 d 11.0 .515 .760 1805 use 10.5 .490 .730 1330 It Wlll be seenfrom the above examples that it 1s poslgg ag 22 :3; sible to attainexcellent magnetic properties in the product without heating the slabsor ingots to a temper- 10.5 .503 .74s 1819 Average ature range whereinliquid slag is formed.

Modifications may' be made in the inventionwithout EXAMPLE lV Two slabsabout 6 inches thick representing two ingots were selected at randomfrom each of six heats with varying amounts of oxygen. These slabs wereheated to a temperature of 2,385 F. or just below the slaggingtemperature and hot rolled rapidly 'to hot bands 0.076 inch thick.Samples representing the center of the coils were processed in thelaboratory. The hot rolled pieces were annealed at l,800 F. for aboutdeparting from the spirit of it.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. In' a method for-producing cube-on-edge siliconiron having a siliconcontentof from about 1.8 percent to about 4 percent andprocesse'dbysteps including hot rolling to intermediate gauge, cold rolling to finalI 2,100-"F. to not more than 2400E .irnmediatel 3 prior to said hot rolling step.

. 2. In a method for producing cube-on-edge silicon- I TABLE [V Pl7;Perm. Heat %C %Mn 705 %Si I %N 700 W/lb. H=l0.

A .023 I .070 .025 3.23 .0060 .0012 I .639 l837 B .0 l 3 .06l .024 3.05.0067 .00! 3 .657 1825 C .022 .047 .023 3.16 .006l .0044 .666 l82l D.020 .052 .020 3.24 .0056 .0064 .730 I760 E .022 .069 .021 3.2l .0052.0070 .90 1695 F .024 .044 .0 l 7 3.13 .0070 .0077 .90 l675 These dataclearly show the verystrong effect of oxyiron having a silicon contentof from about 1.8 percent gen content on the texture and magneticproperties obtainable. The core loss values attained for the sampleslower than those hitherto obtainable.

with oxygen below 0.0020 percent are excellent and' to about 4.percentand processed by steps including hot rolling to intermediate gauge, coldrolling to final gauge, decarburizing and annealing whereby to effectsecondary recrystallization favoring growth of cube onment comprising incombination therewith the step of heating said silicon-iron having anoxygen content no greater than 0.0030 percent to a temperature of from2,100? F. to not more than 2,400 F. immediately prior to said hotrolling step.

3. In a method for producing cube-on-edge siliconiron having a siliconcontent of from about 1.8 percent to about 4 percent and processed bysteps including hot rolling to intermediate gauge, cold rolling to finalgauge, decarburizing and annealing whereby to effect secondaryrecrystallization favoring growth of cube-onedge nuclei by grainboundary energy, the improvement comprising in combination therewith.the step of heating said silicon-iron having an oxygen content nogreater than 0.0045 percent to a temperature of from 2,300 F. to notmore than 2,400 F. immediately prior to said hot rolling step.

'4. The process claimed in claim 1 wherein said silicon-iron has aninitial composition including from about 0.015 percent to about 0.035percent carbon, from about 0.03 percent to about 0.08 percent manganese,from about 0.015 percent to about 0.030percent sulfur, 0.007 percentmaximum nitrogen, 0.008 per- .cent maximum total aluminum and thebalance subcon-iron has an initial composition including from 7 about0.020 percent to about 0.030 percent carbon,

. 12 from about 0.045 percent to about 0.065 percent manganese, fromabout .020% to about 0.025% sulfur, 0.004 percent maximum nitrogen,.002% maximum acid-soluble aluminum, and the balance substantially iron.

6. The process claimed in claim 2 including the step of reacting saidsilicon-iron with sulfur from an external source after said cold rollingand prior to said secondary recrystallization whereby to inhibit primarygrain growth.

7. In a method for producing cube-on-edge siliconiron having a siliconcontent of from about l.8 percent to about 4 percent and processed bysteps including hot rolling to intermediate gauge, cold rolling to finalgauge, decarburizing and annealing whereby to effect secondaryrecrystallization favoring growth of cube-onedge nuclei by grainboundary energy, the improvement comprising in combination therewith thesteps of heating said silicon-iron havingan oxygen content no greaterthan 0.0045 percent to a temperature of from 2,100 F. to not more than2,400 F. immediately prior to said hot rolling step, and reacting saidsilicon-iron with sulfur from an external source after said cold rollingand prior to said secondary recrystallization whereby to inhibit primarygrain growth.

8. The process claimed in claim 7 wherein said cold rolling step is asingle stage reduction to gauge.

2. In a method for producing cube-on-edge silicon-iron having a siliconcontent of from about 1.8 percent to about 4 percent and processed bysteps including hot rolling to intermediate gauge, cold rolling to finalgauge, decarburizing and annealing whereby to effect secondaryrecrystallization favoring growth of cube-on-edge nuclei by grainboundary energy, the improvement comprising in combination therewith thestep of heating said silicon-iron having an oxygen content no greaterthan 0.0030 percent to a temperature of from 2,100* F. to not more than2,400* F. immediately prior to said hot rolling step.
 3. In a method forproducing cube-on-edge silicon-iron having a silicon content of fromabout 1.8 percent to about 4 percent and processed by steps includinghot rolling to intermediate gauge, cold rolling to final gauge,decarburizing and annealing whereby to effect secondaryrecrystallization favoring growth of cube-on-edge nuclei by grainboundary energy, the improvement comprising in combination therewith thestep of heating said silicon-iron having an oxygen content no greaterthan 0.0045 percent to a temperature of from 2,300* F. to not more than2,400* F. immediately prior to said hot rolling step.
 4. The processclaimed in claim 1 wherein said silicon-iron has an initial compositionincluding from about 0.015 percent to about 0.035 percent carbon, fromabout 0.03 percent to about 0.08 percent manganese, from about 0.015percent to about 0.030 percent sulfur, 0.007 percent maximum nitrogen,0.008 percent maximum total aluminum and the balance substantially iron.5. The process claimed in claim 2, wherein said silicon-iron has aninitial composition including from about 0.020 percent to about 0.030percent carbon, from about 0.045 percent to about 0.065 percentmanganese, from about .020% to about 0.025% sulfur, 0.004 percentmaximum nitrogen, .002% maximum acid-soluble aluminum, and the balancesubstantially iron.
 6. The process claimed in claim 2 including the stepof reacting said silicon-iron with sulfur from an external source aftersaid cold rolling and prior to said secondary recrystallization wherebyto inhibit primary grain growth.
 7. In a method for producingcube-on-edge silicon-iron having a silicon content of from about 1.8percent to about 4 percent and processed by steps including hot rollingto intermediate gauge, cold rolling to final gauge, decarburizing andannealing whereby to effect secondary recrystallization favoring growthof cube-on-edge nuclei by grain boundary energy, the improvementcomprising in combination therewith the steps of heating saidsilicon-iron having an oxygen content no greater than 0.0045 percent toa temperature of from 2,100* F. to not more than 2,400* F. immediatelyprior to said hot rolling step, and reacting said silicon-iron withsulfur from an external source after said cold rolling and prior to saidsecondary recrystallization whereby to inhibiT primary grain growth. 8.The process claimed in claim 7 wherein said cold rolling step is asingle stage reduction to gauge.